Pretend for moment that you are riding a sound wave just emitted from oil refinery compressor. You are traveling on a wave in the air at atmospheric pressure and you slam into an acoustic wall consisting of fiberglass, recycled tires, and mass loaded vinyl. Picture what it would be like…More

Katy Payne, while working at the Washington Park Zoo in Portland Oregon, discovered that elephants communicated with one another via infrasound – sound below 20 hertz (Hz). The human hearing range lies somewhere between 20 Hz and 20,000 Hz. The elephants were communicating at frequency levels outside the range of human hearing… More

It has been written that sound bends due to differences in air temperature and acoustic shadows can form. Not much empirical data seems to exist to support this. Perhaps the experiment described above can provide data to support this. I hope that we will be able to do this experiment and share that data… More

Close your eyes for a moment and pretend you are picnicking, during the mid-afternoon, with family and friends in Central Park. About a two football fields away you can see a softball game. You can see the men and women cheering as ballplayers smack the ball and race around the bases. You see a player slide into home plate and you watch the umpire signal him out. You can see all this action, but you cannot hear it. Later that night as the temperature cools and other softball teams are playing under the lights you can see and hear everything clearly. Why is this so? More

Automotive muffler designers use sound physics to reduce the amount of noise coming from automobile exhaust systems. The designers use sound wave interference to cancel out noise. In this article we will explore the concept of sound wave interference and see how muffler designers put to it to work… More

We want to make it easy for you to become a sound pressure mathematical genius. Below you find sound pressure math explained in an easy-to-learn fashion that will make you an authority on sound pressure math. Imagine if someone had laid out tensor calculus for Einstein this way. He may have finished his theory of relativity years earlier. Now let us dive into the wonderful world of pascals, decibels, and other units and see how they relate to sound… More

In 2014 Thermaxx was hired to manufacture sound attenuation jackets for sulfur-recovery compressors located at an oil refinery in South America. Thermaxx tested and ultimately specified a certain combination of materials in order to reduce the compressor noise levels down to the customer’s desired decibel level. Thermaxx engineers conducted the study in a highly sophisticated sound studio utilizing high-tech sound-analyzing equipment and software. The data listed below represents our Engineer’s findings… More

Material manufacturers are required by law to publish Material Safety Data Specification (MSDS) sheets for their products. The MSDS sheet consists of the chemical and physical properties of a particular material like fiberglass or mineral wool. In addition to the MSDS, companies manufacturing materials that target the sound-reduction market often publish sound-reduction coefficients for their materials. The coefficients target individual frequencies. A problem arises when a company wants to offer a combination of materials. You just can’t add up the coefficients for the different materials. There is no formula you can use to determine the combination. The way to determine the coefficient is to test your combination of materials. In this article, we will take you through the testing process and show how the coefficients are calculated… More

In 1970 Congress passed the Occupational Safety and Health Act. The act created The Occupational Safety and Health Administration (OSHA). It granted OSHA the authority to adopt existing federal standards or national consensus standards. In 1968 the American Conference of Government Industrial Hygienists published employee threshold limit values (TLVs) for hazardous substances. In 1971, per the act, OSHA adopted these standards calling them Employee Permissible Exposure Limits (PELs)… More

Wallace Clement Sabine, born in 1868, is considered the father of architectural acoustics. He attended Ohio State University where he physics. He later went to Harvard to pursue his graduate studies. After graduating, he joined Harvard as a faculty member teaching physics. When it came to the study of sound, Sabine never had any formal training. He became fascinated with how sound differed from one lecture hall to another. Along with his assistants, he began moving materials to different lecture halls to see what materials made the lecture halls sound better. Sabine and his assistants spent many nights moving materials and measuring sound waves; he and his team used an organ and a stop watch to measure the deterioration of sound as it passed through the lecture hall… More